1. Field of the Invention
The present invention relates to a valve operating system in an internal combustion engine, comprising a switchover pin which is movable between an associatively operating position where adjacent ones of rocker arms are operated in association with each other, and an associative-operation releasing position where the associative-operation is released, the switchover pin receiving at axially opposite ends thereof a hydraulic pressure force acting toward the associatively operating position and a spring force acting toward the associative-operation releasing position, a cylindrical roller shaft which is fixed to one of the adjacent rocker arms, and into which the switchover pin is slidably fitted in response to the movement thereof toward the associatively operating position, and a roller rotatably carried on the roller shaft to come into rolling contact with a cam provided on a camshaft.
2. Description of the Related Art
Such a valve operating system is conventionally known from Japanese Patent Application Laid-open No. 11-13440 and the like, for example.
Such valve operating system is designed such that the operational characteristic of an engine valve is changed in accordance with the operational condition of an engine by switching-over a state in which adjacent rocker arms are swung independently from each other, and a state in which the adjacent rocker arms are swung in association with each other, by operating the switchover pin between the associatively operating position and the associative-operation releasing position. However, the weights of the rocker arms are increased due to the provision of such a switchover mechanism. Therefore, it is a conventional practice that each of the rocker arms is formed of an aluminum alloy to have a decreased weight.
It should be noted here that there is a possibility that the hydraulic pressure force for biasing the switchover pin toward the associatively operating position may be varied. When the hydraulic pressure force is varied in a state in which the switchover pin has been moved to the associative-operation releasing position with the hydraulic pressure force lowered, the switchover pin may be moved toward the one rocker arm against the spring force in some cases. In the known system, however, the end surface of the roller shaft fixed to the one rocker arm is disposed flush with the opposite side surfaces of the one rocker arm, so that the switchover pin is slidably fitted into the roller shaft in response to the movement thereof toward the associatively operating position. When the adjacent rocker arms are swung relative to each other in their states in which their associative-operations have been released, there is a possibility that the end surface of the switchover pin may also be brought into sliding contact with the side surface of the one rocker arm, and a wear powder produced due to the sliding contact of the switchover pin with the rocker arm may enter into the roller shaft to impede the smooth switching-over operation of the switchover pin.
The present invention has been accomplished in view of the above circumstances, and an object of the present invention is to provide a valve operating system in an internal combustion engine, wherein a wear powder can be prevented from entering into the roller shaft, thereby ensuring the smooth switching-over operation of the switchover pin.
To achieve the above object, according to a first aspect and feature of the present invention, there is provided a valve operating system in an internal combustion engine, comprising a switchover pin which is movable between an associatively operating position where adjacent ones of rocker arms are operated in association with each other, and an associative-operation releasing position where the associative-operation is released, the switchover pin receiving at axially opposite ends thereof a hydraulic pressure force acting toward the associatively operating position and a spring force acting toward the associative-operation releasing position, a cylindrical roller shaft which is fixed to one of the adjacent rocker arms, and into which the switchover pin is slidably fitted in response to the movement thereof toward the associatively operating position, and a roller rotatably carried on the roller shaft to come into rolling contact with a cam provided on a camshaft, wherein at least one of axially opposite end surfaces of the roller shaft formed of a material harder than that of the one rocker arm, which receives the switchover pin, protrudes from a side surface of the one rocker arm.
With such arrangement of the first feature, the end surface of the roller shaft fixed to one of the rocker arms, which receives the switchover pin, i.e., the end surface adjacent the other rocker arm protrudes from the side surface of the one rocker arm. Therefore, even if the hydraulic pressure force is varied during relative swinging movements of the adjacent rocker arms, the end surface of the switchover pin cannot be brought into sliding contact with the side surface of the one rocker arm, and is brought into sliding contact with the end surface of the roller shaft. The roller shaft is made of the material harder than that of the one rocker arm and hence, it is possible to prevent the generation of a wear powder due to the sliding contact of the roller shaft and the switchover pin to the utmost, so that the wear powder cannot enter into the roller shaft, thereby ensuring the smooth switching-over operation of the switchover pin.
According to a second aspect and feature of the present invention, in addition to the first feature, an outside diameter of the roller shaft is set so that a change in position of the switchover pin relative to the roller shaft in response to the relative swinging movements of the adjacent rocker arms in a state in which the switchover pin is in the associative-operation releasing position, occurs within a range defined by an outer periphery of the roller shaft. With such arrangement of the second feature, during the relative swinging movements of the adjacent rocker arms, the change in relative position of the switchover pin relative to the roller shaft occurs within the range defined by the outer periphery of the roller shaft fixed to the one rocker arm. Therefore, even if the hydraulic pressure force is varied during the relative swinging movements of the adjacent rocker arms, the end surface of the switchover pin cannot be separated from the end surface of the roller shaft to come into sliding contact with the side surface of the one rocker arm, and is brought into sliding contact with the end surface of the roller shaft.
According to a third aspect and feature of the present invention, there is provided a valve operating system in an internal combustion engine, comprising a switchover pin which is movable between an associatively operating position where adjacent ones of rocker arms are operated in association with each other, and an associative-operation releasing position where the associative-operation is released, the switchover pin receiving at axially opposite ends thereof a hydraulic pressure force acting toward the associatively operating position and a spring force acting toward the associative-operation releasing position, a cylindrical roller shaft which is fixed to one of the adjacent rocker arms, and into which the switchover pin is slidably fitted in response to the movement thereof toward the associatively operating position, and a roller rotatably carried on the roller shaft to come into rolling contact with a cam provided on a camshaft, wherein an outside diameter of the roller shaft formed of a material harder than that of the one rocker arm is set so that a change in position of the switchover pin relative to the roller shaft in response to the relative swinging movements of the adjacent rocker arms in a state in which the switchover pin is in the associative-operation releasing position, occurs within a range defined by an outer periphery of the roller shaft.
With such arrangement of the third feature, during the relative swinging movements of the adjacent rocker arms, the change in position of the switchover pin relative to the roller shaft occurs within the range defined by the outer periphery of the roller shaft fixed to the one rocker arm. Therefore, even if the hydraulic pressure force is varied during the relative swinging movements of the adjacent rocker arms, the end surface of the switchover pin cannot be separated from the end surface of the roller shaft to come into sliding contact with the side surface of the one rocker arm, and is brought into sliding contact with the end surface of the roller shaft. The roller shaft is made of the material harder than that of the one rocker arm and hence, it is possible to prevent the generation of a wear powder due to the sliding contact of the roller shaft and the switchover pin to the utmost, so that the wear powder cannot enter into the roller shaft, thereby ensuring the smooth switching-over operation of the switchover pin.
The above and other objects, features and advantages of the invention will become apparent from the following description of the preferred embodiment taken in conjunction with the accompanying drawings.